text:
In the gyroscopic precession left turning tendency, why does a pitch down cause a forward force at the top of the propeller?
I'm a student pilot, and all the textbooks and online resources I'm reading show a pitch down as a forward force acting on the top of the propeller (causing the resulting forward force on the right side of the prop, thus a left yaw). Where does this force come from? Isn't a pitch down a downward force on the prop hub, since the rotation is occurring about the airplane's center of gravity (behind the prop)?

The prop is a big gyro.  It's the gyroscopic precession force created at the propeller when it's subjected to an input changing its axis of rotation, where, as with any gyro, the inertial resistance to the change in axis acts at 90 degrees rotationally to the input.
The airplane pitches down, rotating the axis (extending forward) of the propeller down, acting through the hub.  Being a gyro that is being forced to change its axis vertically, it results in precession feedback acting through the hub at 90 degrees (as if there was a thrusting force at 3 o'clock), yawing the airplane to the left.
It doesn't matter where the prop's axis is in relation to the rotational axis of the airplane in pitch, just that its axis changes as the airplane pitches.
The best way to experience it is to take off in a tail dragger with a large prop, like a Cessna 180, and force the tail up early in the takeoff run before the rudder is having any effect.  The swing to the left from propeller precession is pretty strong.

Oh I see, so the "force" at the top of the prop is actually just a representation of the rotational acceleration about the longitudinal axis of the prop. Your second paragraph is exactly what I was looking for. Many thanks!

Grab a bicycle wheel, get it spinning, then try to change its plane of rotation.
Rotating objects (such as a frisbee) tend to stay in the same plane of rotation, indeed, this is what makes them valuable as orientation references when visual cues are lost.
A spinning prop is no different in its behavior.  When you pitch down, you are changing
the plane.  One way to see it is to consider the prop as a spinning disk.  When you tilt it,
the parts of the disk 90 degrees from where you tilt experience the greatest change in direction.  This is why pitching at 6 and 12 o'clock produces yaw at 3 and 9 o'clock.
It is the rotational energy of the disk changing direction that causes the yaw.

There is not actually any force applied at the top of the propeller. This is just a shorthand way of describing the effect of the rotational inertia of the propeller. The propeller is initially spinning clockwise around the axis pointed straight through the spinner. Nothing is spinning in the other two perpendicular axes.
Mathematically, we can represent angular momentum with a conventional direction where angular momentum in the direction $\rm\hat x$ corresponds to rotation in a clockwise direction as viewed if you were to face in the direction $\rm\hat x$.
The propeller has an angular momentum of $ L = I\omega \rm\hat x$, where $I$ is the "moment of inertia" of the propeller (essentially how much inertia it has), $\omega$ is the rotational speed of the propeller in RPM, and $\rm\hat x$ represents the axis that goes forward through the spinner.
Now introduce a pitching moment, is lowered by a small angle ${\rm d}\theta$ in a short time ${\rm d}t$. After this short time, the new angular momentum of the propeller will be $ L = I\omega({\rm\hat x} - {\rm\hat z\,d}\theta)$, where $\rm\hat z$ is the upward direction.
But angular momentum cannot be created or destroyed, so this has to come from somewhere. Where it comes from is the rest of the plane: after the same time ${\rm d}t$, then, it has gained angular momentum of $dL_{\rm plane}=I\omega{\rm\hat z\,d}\theta$, so that the total angular momentum $L+L_{\rm plane}$ is unchanged. This manifests as a torque on the plane directed along the $\rm\hat z$ axis equal to the time derivative of the plane's angular momentum:
$$ \tau=\frac{{\rm d}L_{\rm plane}}{{\rm d}t} = I\omega{\rm\hat z}\frac{{\rm d}\theta}{{\rm d}t} $$
This torque creates a clockwise motion as viewed from below the plane (i.e. looking up, along the $\rm\hat z$ axis), or in other words a yaw to the left.
In short, by pitching the propeller down you are "creating" counter-clockwise angular as viewed from below the airplane, and the plane has to rotate clockwise in order to balance it out and conserve angular momentum.


text:
Can I carry a waveform generator with me inside an airplane?
I have recently learned that I have an urgent domestic flight tonight. I am curious about whether I can carry the device with me. The device I want to carry is 33120A Arbitrary Waveform Generator. I will appreciate any help.

If it requires wall power and has a removable power cord, remove the cord. If it's a standard 3-prong PC-style cord, it's highly likely they'll have one you can borrow at your destination. If not, have a coworker carry it in his/her luggage (assuming someone else is traveling with you). If it's battery powered, leave the batteries at home and tell them to get you some at your destination. It can't cause harm if it can't be turned on.

Having a business card with "engineer" in the title works wonders.

You did not specify a country for your domestic flight, but in general:
Assuming you do not intend to power it on and use it during the flight, it should not be a problem.   Esoteric and unusual electronics may get a bit more screening by security services, but should not be explicitly banned.
I recommend allowing extra time for security screening, and it may help if you have instruction manuals and other documentation to help security understand what the device is and why it is not a threat.

Also they may want you to fire it up.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Are throttleable rocket engines the less efficient the lower the power setting?
Are throttleable rocket engines less efficient the lower the power setting? Logically that would lead to lower pressures in combustion chamber and so lower thermodynamic efficiency. Or is it remedied by combustion chamber design?

Did you perhaps mean to post this on space.stackexchange.com?

There are numerous questions here about engines, and this is pertaining to rocket powered interceptors, I think it fits here. It's not  usual to throttle spacegoing rockets save for vernier engines

You've just posted a question about jet engines in Space SE and here's a question about rocket engines in Aviation SE. I'm voting to close both and hopefully you'll get both of them in the right location. If these are the right locations, there won't be further votes and mine will expire. By the way these days practically all rocket engines going to space are throttle-able, and a quick check of questions in Space SE will show this. This shows 200 posts: https://space.stackexchange.com/search?q=throttle

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
How do airblast fuel atomisers work?
How do airblast fuel atomisers work? Do they simply inject fuel with high velocity? Against the flow or perpendicular to it? How is the fuel jet shaped?


text:
Carrier VTOL takeoff or not?
In this picture, shown in a recent news article, a "shooter" seems to be giving a "go forward" command to what I believe is a Lockheed-Martin F-35 aircraft already prepped in a VTOL configuration. But since VTOL's take off and land vertically, under what circumstances would a shooter give the pilot this "go forward" command?

The rolling takeoff is a STOVL or Short Takeoff and Vertical Landing operation.  The F-35B is too heavy to hover with full fuel and a warload, but can use its vertical lift system to augment lift generated by the wings allowing an F-35B to lift off in less than 500ft ground roll with a Vr of around 70 knots or so.  The procedure is also used by Harriers flying off assault ships as well.  Some carriers likes the Royal Navy’s HMS Queen Elizabeth make use of a ‘ski jump’ to augment the takeoff roll and launch the aircraft upwards, allowing for a greater launch load and/or shorter takeoff roll.
Once the warload and at least 60% of the total fuel capacity has been depleted, the F-35B can enter into a full hover and land vertically.  This allows the F-35B to recover on an assault ship without the use of arresting gear.
An additional variant of the F-35, the F-35C, has a larger wing and tailplane, different landing gear and an arrestor hook in the tail.  This allows it to launch and recover aboard larger CATOBAR aircraft carriers, but cannot do so aboard assault ships like the F-35B can.
The pointing signal by the launch officer is the takeoff signal.  It can be used as instructions to fire the catapult/EMALS or for the pilot to release brakes and make a short takeoff, as in this case.

What is this "warlord" you speak of?

According to this chart from the Navy the signal officer may simply be giving the generic takeoff signal (or at least completing it).

The F-35 is capable of doing traditional catapult launches as well as VTOL takeoffs but there were some deck heat related issues with the VTOL takeoffs.

Yes, this is correct.  It is not a "taxi forward" signal, but a "cleared to launch".  I am not familiar with VTOL operations, but would presume this would initiate pilot action, where this same signal by the shooter on a traditional catapult ship, (that I am familiar) would trigger the Catapult Officer to fire you off the end.

They usully don't take off vertically, but use a rolling takeoff instead. They accelerate forward before going up, as this generate lift using the wings plus the engine allowing a higher load of fuel and payload.


text:
How are forward and aft CG limits calculated?
I have been tasked to create a POH for my aero engineering coursework and part of this task is to create the CG envelope for the theoretical 65 passenger aircraft. I have figured out weight, moment and cg for all loading scenarios but I am wondering how to create the actual envelope using forward and aft limits, as surely not all these scenarios will be able to fly? TIA

Aft CG is primarily stability margin (say, 10%). For forward CG, you can use the ability to rotate at V_rotate as a good approximation.

For conceptual design, the longitudinal CG limits can be evaluated with:

Static Margin: you probably want at least 10% static margin at aft CG at the early conceptual stage for at least the flaps in configuration.
Trimmability: the amount of elevators or stabilizer (if movable) required to trim both full power and power off, for all flaps. For tail mounted engines, full power may limit the forward CG; for wing mounted engines, full power may limit the aft CG.
Takeoff Rotation: ensure your aircraft can rotate at $V_R-10kt$ or $V_R-7\%$ at takeoff flap at forward CG. This assumes the landing gears are positioned to give adequate tip-over margin.

Once you are in the preliminary design, then you have lots more things to look at.

You have done half of the way. Since you have computed the CG variations in all loading scenario, you know approximate limits. This limits are the ideal limit from loading and unloading point-of-view. But in real application, the design of the aircraft does not allow such broad limits.
There are many factors that limits the aircraft aft CG movement:

MLG load: The loads on MLG increases as the aircraft weight is increased or the CG is moved aft. Since in most of cases, the MLG's are designed for touch down loads at maximum landing weight, which is lower that the maximum ramp/take-off weight, the static loads at maximum ramp weight may exceed the dynamics load at touch down. So, a limitation may be imposed on aft CG location regarding this issue.
Take-off Tip-Up: At the take-off conditions, the engines are producing their maximum thrust. If the engines are located below the CG, which is the case for under-wing mounted engines, this thrust produces pitch-up moment. This pitch-up moment reduces the load on the NLG. From the other hand, as the aircraft weight decreases combined with aft cg movements, the load on the NLG will be further decreased. At light enough NLG loads, steering effectiveness is reduced, and eventually, the NLG load can become negative causing the airplane to tip up. So an aft CG limits may be imposed to maintain enough loads on the NLG.
Static Stability: Too far aft CG may cause neutral or negative stability, so a margin (normally 10% of MAC) should be provided between the CG and the aerodynamic center.
Go-Around: At go-around condition, the engines are producing the maximum thrust, and a huge pitch-up moment. Elevator deflection are required to counter this moment with pitch down moment. This moment is proportional to amount of upward acting load on the tail a the arm of this acting load. The distance between the tail and the CG is the arm. As the cg moves aft, if the tail reaches its maximum lift the aircraft can not maintain its path. So a limit may be imposed to prevent pitch-up at go-around.

By combining the above limits, and other limits that may arise from that specific configuration, an aft CG limit can be estimated.

Another is the ability to stall the aircraft (forward CG limit). Stick force during go-around could also limit the forward CG is the engines are tail mounted.

Of these, (3) is by far the most important and should be #1. Other things sometimes may be a factor that imposes further limit, but static stability always applies. Sometimes, the aft limit is imposed by things like spin recovery, but it's broadly the same category. (4) is not practically an issue: the arm change is not very significant (esp. for aircraft with underwing engines), while reduction of the aerodynamic moment due to relaxed stability is. It is the forward limit (which you didn't cover) that is largely determined by controlability (i.e. available elevator control).


text:
What is an example of a system like MCAS?
The related question "Is it common for automated control systems to use non-redundant sensors?" does not ask about a specific example, nor are specific examples provided in the answer.
The criteria for my question:

Activates on its own, or always active.
No light/text indication of it being active.
No specific disable switch.
Relies on 1 sensor when 2+ exist.
The system is not disabled when the 2+ sensors disagree.

As you can see, these properties are modeled after what is known about MCAS.
This question isn't about the 737 in particular but about any commercial (fly-by-wire or not) airplane, so eventually the answers should specify the model, and if possible the justification of the design.

Neither 737 MAX?

"Fixed". Indeed it doesn't matter if it is fly by wire or not.

To simplify, it's not about the lack of redundancy, but for the presence of redundancy which isn't used; e.g., 2 (or more) AoA sensors, but the system uses only one.

The Q text seems to address this N-sensors-but-1-used thing — if one disregards the other more strict criteria/properties in my Q — but does no ask for other example. I don't know if this isn't enough to qualify mine as not a duplicate. For now I hold that it's a different question.

So, basically, ignoring all the rest that could have made a difference, those 5 duplicate-watcher are saying that if I want to ask for examples, I need to edit that duplicate answer. Interesting.

I wanted to be precise to avoid answers like "the autopilot" or alike. Reading just the title isn't a good sign, and if one can't/don't want to read the tedious list, he or she could at list skip the question and leave it alone, or comment as you did suggesting to make it briefer and clearer.

Maybe closer, but it searches for reasons (I am not), not for “names” of (sub)systems. (I am used to be enough aware of what I am searching and asking for, so I don't get the underlying part.) Also, I want to exclude (sub)systems you won't be able to fly without (like in the F-16). (Again, think about MCAS: if it didn't exist, you could anyway fly — and even likely avoid by your own the stall situation it should have helped with... but this wouldn't be in my criteria or it'd seem there's an underlying assertion about that system being unuseful.)

I really appreciate your efforts! I was going to modify it by myself — though likely I haven't the gift of brevity you have — needed just more time which I can't use now. Thanks alot again for your time! Let's see if it works and someone comes with an answer.

Irrespective of 737 MAX MCAS, I haven't seen similar decision relying on a single sensor on 777 or on 757.
Similarly I found nothing similar on Airbus 320, 330, 340, 350, or 380. On these Airbuses, 3 sensors are used for critical decisions, thus the faulty sensor is isolated by voting the data. If the 3 sensors are diverging (no 2 sensors giving similar data), the system goes into safe degraded mode, and the pilots are informed by automatic displayed message.

I’m not surprised. Aeronautical engineering 101: never rely on only one single input if it can cause loss of control.

There's another puzzling matter rambling in my mind and that I feel (maybe wrongly) it should be 101 fact: if the autopilot disconnects because of sensors disagreement, any other automatic system which uses one of those now-disagreeing sensors should be disconnected too (with loud warnings or whatever): disconnecting the autopilot but needing an active action by the pilots to disable those other systems seems very illogical to me.

If I understand, you believe, it would have been better to inhibit automatically any MCAS trim in case of AOA disagree, probably it will be like that in the future when the aircraft will be allowed to fly.

@ShinTakezou That would make those systems dependent on (in this case) the autopilot, which seems to me to add to the possible failure modes. What if it's the autopilot code that reaches the wrong conclusion for whatever reason, and not a problem that would affect other systems? You risk suddenly disconnecting a whole slew of perfectly working systems, throwing warnings and errors at the pilots as you go. Take something like QF32, but made worse by the plane actually acting up beyond spewing messages at the flight crew. Basically pretending that a system doesn't exist seems the worse approach.

@aCVn No, it would make activation of both systems dependent upon correct functionality of the sensors.

@aCVn  I am not saying B should disconnect if A does in the sense that A is driving the disabling of B; I was saying B should disconnect on the same (subset of) conditions A disconnects — I hope the difference I am making here is clear.

I hope they will put 3 AOA so that disagreement, full disagreement, becomes improbable in a single flight before maintenance action, nevertheless assuming we get disagreement and the autopilot disengages, what’s the problem if MCAS is not active too! A normally flying pilot doesn’t need the MCAS to fly 737 NG. Why will he need the MCAS for the max. If the MCAS is just to hide a defective pitch stability, this plane should not fly unless they install,  why not, 4 AOA.

For better understanding please refer to the following website: https://www.nytimes.com/2019/06/01/business/boeing-737-max-crash.html

It should be noted, that Airbus (A320, but possible with all later types too as the logic is basically the same) even had at least one incident where two-of-three AoA sensors agreed, but were the wrong ones (because they froze), and triggered alpha-limit (pitches the aircraft down similar to the MCAS). However the pilots were properly taught how to force the system in alternate law (disable the protections) and in Airbus doing so does not otherwise affect handling of the plane.

@JanHudec There also has been a case of all 3 AOA probes stuck at the same angle on an A320 and the aircraft subsequently being lost from a check flight because crew tried to demonstrate the (now defunct) low speed protection...

@CptReynolds, yes, but that case only caused undetected failure of protection, not spurious pitch changes, and thus wouldn't be a problem on normal flight. The spurious alpha-limit case is more similar to the issue in question.

Speed Trim System (STS) is very similar to MCAS and is used on the same aircraft. Moreover, Boeing maintains that it did not have to notify pilots about MCAS because MCAS is a part of STS, running on the same computer and controlling the same surface — the stabilizer.
In a way, MCAS is just an extension of the system that already existed on prior versions of the 737. Just like MCAS, STS can cause stabilizer to run away, and if pilots catch it too late, they can get themselves into a situation similar to Ethiopian Airlines Flight 302, because the recovery procedure is the same.
Recently it has been reported that another glitch had been found in the 737 MAX software. The details are sketchy, here is what the Seattle Times reports:

Exercises on a Boeing 737 MAX simulator in recent days showed pilots
  might have difficulty responding to the newly identified failure. Just
  as MCAS uses a motor to move a small wing at the tail of the plane to
  lower the nose, the latest issue could prompt that same wing to move
  without pilot commands. The tail wing is known as a horizontal
  stabilizer.

To me this looks like a bug with STS software. Because STS is used on earlier 737 versions, Boeing does not seem to appreciate too much noise around this issue, because it may affect the entire 737 fleet.

About MCAS being part of STS, I bookmarked this where you read: “Elwell clarified that MCAS is not an anti-stall system, but a supplement to the speed-trim system”. Anyway for some reasons this STS unextended by MCAS didn't cause too much trouble in the past, it seems. Maybe it has less authority?

@ShinTakezou Yes, has less authority. Also, on the NG a pilot can turn STS off while keeping electric trim switches operable. On the MAX it is not possible. So yeah, even if STS goes haywire on the NG, there is better chance to recover than on the MAX — if pilots know about the function of EACH switch, because the recovery procedure tells them to turn BOTH switches off. I think they will know it now after the crashes. I expect Boeing to re-wire stab trim cutoff switches on the MAX to the NG configuration if it wants to fix the issue the way it should be fixed.


text:
What happens when a person dies during the flight? What kind of procedures exist regarding deceased passenger on board?
I was just reading about a young woman who died on the long haul flight from LA to Melbourne. Heartbreaking. Young life cut short. RIP. But this horrible situation made me wonder about a presence of a deceased passenger on board. the article says that she died mid-flight. So there could be another remaining 8 hours of flying. I wonder if there are any regulations on how to proceed with a deceased person on board. where would they put her body? I am sure they probably covered her but still, where would she remain for the rest of the flight? I dont think they would put her back on her seat, and not sure if it is ok just to put her on the floor by the kitchen/bathroom areas. I am sorry i know it is weird but seriously does anyone know if there are any provisions regarding logistics of that kind of unfortunate situation?

I feel as if there is a duplicate of this question somewhere but I can’t find it.


text:
does a semi sphere have more drag in comparison to a flat plane with equal surface area?
What the title says, some things to know is that these aren't solid shapes, think of a bowl and a sheet of wood.

Related on Physics.SE: What shape has the highest drag coefficient?

Ask more questions

No it doesn't. This chart explains how.
https://www.researchgate.net/figure/Typical-drag-coefficients-for-regular-3-D-objects_tbl2_273771608

I read somewhere that the lowest drag streamline body has a fineness ratio of 3:1, surprisingly stubby.  The short and odd looking Questair Venture came every close to this ideal shape  http://www.questairventure.com/


text:
What is the purpose of the selected altitude/airspeed in ARINC 429?
What is the purpose of the selected altitude and airspeed fields in ARINC 429?

Both labels are used to transmit the altitude and airspeed that are dialed into the Mode Control Panel of the autopilot. They are not necessarily the current altitude/airspeed, instead they are the target values that the autopilot is steering to.

so what is the altitude selected based on altitude? ground or sea level?

It is based on the barometric altitude of the pilot flying. So pressure altitude corrected for the altimeter pressure setting.

Thank you for help

@LeoAnggaraKrisna The current and selected altitude can be pressure (FL), true (MSL) or absolute (AGL). The autopilot doesn't care which; it will just fly the plane up or down as needed to make current equal selected.

DeltaLima very nicely covered the "what" of these labels. As to the "why", I have three examples of their uses:

Autopilot setpoints (altitude, airspeed, heading) are displayed on the Primary Flight Display for the pilot's situational awareness (and so that she knows when to stop when twiddling the autopilot control knobs)
They can be logged to a Flight Data Recorder for accident investigations, or a Quick Access Recorder for operational / maintenance purposes
They're transmitted by certain types of Mode S transponder with "Enhanced Surveillance" capability. If ATC is also suitably equipped (e.g. a lot of Eurocontrol airspace) the preselected altitude is displayed on their scopes and helps to prevent altitude busts due to miscommunication or pilot error.


text:
Would using a drone to pay for something count as commercial use?
If I were a drone hobbyist, and I flew a drone over to someone to give them money in exchange for something, would that count as commercial use and therefore be illegal? Here’s an example scenario:
I’m not licensed to fly drones commercially. I fly a drone with money and an order over to the local McDonald’s drive-through with some money. The cashier takes the money and puts a burger into the basket in return.  Assuming the McDonald’s is just across the street (still in visual range) and there’s no one in the drive-through that I’d be flying over, would that be legal? I’m not operating the drone for hire, and since I’ve payed for the burger, it’s my property (so I’m not illegally flying someone else’s property).
I certainly don’t intend to do this (and I am a commercial drone pilot), but I was just wondering if that counts as commercial use.  I couldn’t find anything specific in the regulations that explained it.

Well, first, you need to get caught...

Laws around drone use are very new, and the only way to be certain about this is to have a case come to trial. You probably don't want to be the person it comes to trial over. A lawyer would give you a much better interpretation, but even they can't be sure.
If you are interested in my personal uninformed opinion (IANAL) then I think it would not count as commercial use. My reasons are:

The drone is completely incidental to the transaction. The cashier would do exactly the same if you showed up in person on foot or in a car, or if you sent someone else to make the transaction.
If you drive your car to McDonalds, that does not count as commercial use of your car. If you fly to McDonalds  then that does not count as commercial use of an aeroplane.

100% correct in your reasoning.


text:
How do changes in flight affect L/D max and the speed at which I must travel to maintain it?
I have an plane flying at L/D max and I want to maintain L/D max.
Firstly, if this plane burns through a portion of fuel and becomes lighter, how would I have to change the speed to maintain it?
My thoughts are that because the plane is ligher, less lift is required to keep it level and therefore Cl decreases, decreasing L/D and therefore I'd have to increase speed?
Also, how would an altitude drop affect L/D max?
I assume because of the higher density of air, you'd get more drag and therefore, lower L/D as such, would need to speed up to maintain?
Also, extending speed breaks during landing - again i assume because this increases drag you would need to speed up to get back to max ratio.
I'm quite confused with this concept and what parameters affect what.

The best way to fly a constant L/D max is to have an angle of attack indicator.  Otherwise you would be constantly re-calculating the best speed as you burned fuel and changed weight.  Because most most GA aircraft don't have AOA, and are not too dramatically affected by changes in weight, max range and max endurance are generally expressed as an airspeed.
For a constant L/D max AOA, airspeed would actually decrease as the plane got lighter.  Think about the fundamental forces acting on the aircraft - lift is produced by a combination of airspeed and AOA.  If AOA remains constant, less airspeed will be required to produce the lift needed to counter the weight as the airplane gets lighter.
The reverse is true of course, if you are flying a constant airspeed you would need to gradually trim nose down to a lesser AOA as the aircraft gets lighter to prevent it from climbing.
Regarding speedbrakes, they add drag so if you want to speed up you would not extend the speed brakes.  Speedbrakes are used to slow down, or to maintain a given airspeed at a higher power setting to improve throttle response and go around capability (upon retraction) during approaches.


text:
What's an "altitude engine"?
FAR 91.205(b)(8) says that you need a manifold pressure gauge for each "altitude engine", whatever that means.
What's an "altitude" engine?

An altitude engine is a type of engine that uses a turbocharger (and less often, a supercharger) to generate sea-level pressure in its intake manifold, up to its critical altitude, at which point power will start to fall off.
Non-altitude engines will lose power as they climb because the ambient air pressure drops off at a rate of about 1" Hg per 1,000 ft of altitude (up to 10,000ft).
The altitude engine allows aircraft to fly at higher altitudes at full power, and increases the aircraft's speed and efficiency, because true airspeed increases with altitude. It also allows an aircraft under IFR to fly at higher MEAs or under VFR over higher terrain, and allows the pilot to choose a favorable altitude for weather.
The first kind of altitude engine is called a turbocharged engine, which can generate more intake manifold pressure than at sea level. For example, a Mooney Bravo M20M can generate 36" of manifold pressure, and can generate at least 30" of manifold pressure up to its critical altitude of 22,000ft.
The other kind of altitude engine is called a turbo-normalizer, which develops a maximum of sea level pressure: 30”Hg or 1 Bar. These engines will perform as well at altitude (up to their critical altitude) as they do at sea level.
A turbo-normalized engine is considered less taxing on the engine than a turbocharged engine because the former doesn't develop above sea-level pressure or high turbine-inlet temperatures. The turbo-normalized engine is also easier to fly than a turbocharged engine, since it never develops more power than would be developed at sea level.
All altitude engines also typically have a controllable-pitch prop, and develop more than 200 horsepower, so they would require both a complex aircraft endorsement and a high-performance endorsement. See 14 CFR Part 61.31.

"The altitude engine is also easier to fly than a turbocharged engine, since it never develops more power than would be developed at sea level." Am I missing something? The answer starts off saying an altitude engine uses a turbo, but this quote says they're different.

@zymhan I updated the answer to make it clearer

FAR 1 says that an altitude engine is

a reciprocating aircraft engine having a rated takeoff power that is producible from sea level to an established higher altitude.

Basically, if you can develop sea level power at an altitude higher than sea level, you've got an altitude engine.  Generally, this means you're flying with a boosted engine (whether the boosting comes from a turbo, a supercharger, or something else).

The air going into the engine has a higher pressure than the ambient air.

The quote doesn't say "sea level power": it says "take off power". Doesn't that just mean that, it can take off from airports above sea level?

What could the "something else" be that boosts power? An electric motor (as in battery powered engine, electric car style, but that's probably not reciprocating anymore)?

@Xen2050 superchargers are typically electric. turbochargers are exhaust-driven. not sure what "something else" is either.

@ChrisW the M20M can generate 36"MP takeoff power, but only generates 30" at its critical altitude. So either the quote is wrong (or just out of date), or my engine is wrong, or "an established higher altitude" doesn't refer to "critical altitude"

@Xen2050.  My Cessna 340 with RAM VII was capable generating nearly 38 inches of MP  at take off.  Normal operation (not in takeoff) was limited to 36 inches.  The TSIO-520-NBs use exhaust driven turbochargers.

@rbp I've only seen belt-driven superchargers (like Mad Max's car :) But I was thinking of a full batteries & electric-only motor, no fuel burning at all, like in a Tesla electric car

NB: Wikipedia says common usage for "supercharger" is that it is mechanically-driven, and "turbocharger" for exhaust gas driven. http://en.wikipedia.org/wiki/Supercharger

An altitude engine is one that is either supercharged or turbocharged. It creates its own level of density altitude inside its INTAKE manifold. This makes the engine produce more power and more consistent power regardless of the atmospheric/environmental actual density altitude.
The difference between supercharging and turbocharging is the method you generate the higher amount of pressure (or LOWER DENSITY-ALTITUDE) inside your intake manifold.
Turbochargers have an impeller fan just past your EXHAUST manifold that is spun by the pressure of the exhaust gasses escaping your cylinders before reaching the muffler. That is connected to an impeller located between your INTAKE manifold and the fresh air cleaner/filter. That impeller drives or boosts the amount of air going into your engine, increasing its pressure.
Superchargers are air pumps (think industrial pump and not bicycle nor shop pump) that are attached directly to your INTAKE manifold. They are connected to your crankshaft usually via a system of belts and clutches just like your alternator, water pump, air conditioning pump, hydraulic pump, or engine driven fuel pump (depending on the model).
Turbochargers are typically smaller in size and lighter in weight. But, they are exposed to very high heat and RPMs promoting more wear and tear.
Superchargers typically take up much more space and weight. But, they are only exposed to ambient engine heat and their own internal friction. They spin at lower RPMs to produce the amount of air volume pumped or boosted into the INTAKE manifold to increase pressure. The mechanically driven pump theoretically has less wear and tear.
Either one boosts the pressure in your INTAKE manifold beyond what is in the ambient atmosphere. Air is being blown/forced into your engine as opposed to having the engine suck in the air it needs. Like a water hose instead of a straw or a ventilator instead of your lungs, your engine is being force fed.
Either way, it is not the increased pressure in your INTAKE manifold which is truly important. Nor is it the increased volume of air. It is the increased amount of oxygen molecules provided by either INTAKE system for combustion with the fuel in your cylinders that makes the difference. Air density (or to be more precise, oxygen density because the percentage of oxygen will be consistent regardless of pressure or volume) is the true goal of both systems. Since both systems will cause the air to heat up adiabatically (increasing the pressure of and/or decreasing the volume or available space for a gas will cause an increase in temperature), that is why many systems will incorporate an inter cooler (air cooler located between the turbo/supercharger and the INTAKE manifold) into the INTAKE system. The cooler the air, the greater the air density.
THE DENSER THE AIR/OXYGEN-IN-THE-AIR, THE MORE POWER/THRUST YOU GET FROM YOUR ENGINE.
Sorry for the long explanation. ;)

Welcome to Aviation.SE!  Can you perhaps clarify how this answer answers the question at hand?

Welcome to Aviation.SE! If you haven't already done so, I'd like to invite you to take our [tour] and read the [help]. As dalearn says, I don't see how this actually answers the question "what's an altitude engine?". Perhaps you could edit your answer?

A simple edit and its now a good answer so +1 from me! You maybe interested in looking at this page on formatting/markdown for how to use bold rather than all caps.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
What is the main difference between 'continental fuel injection system' and 'Bendix RSA fuel injection system'?
While I'm studying Aircraft Engine system, I learned that there are two dominant kinds of fuel injection system : 'continental fuel injection system' and 'Bendix RSA fuel injection system'
I tried to find the main difference between those systems, and all I found out was that the former one injects fuel before the each cylinders, in the manifold(with nozzles connected to manifold valve assembly), and the latter one injects fuel directly into the each cylinders(and the nozzles are connected to a fuel divider). But I'm not sure this is true or not, since there are no part that explains the exact difference between them.
Could anyone let me know about this?

First of all, both of these systems are continuous flow fuel injection systems, therefore they do not inject fuel directly into the cylinders. Since the fuel is flowing continuously from the injector nozzles, the spray is directed into the induction system just before the intake valve. That way, the fuel will only enter the cylinder when the intake air charge is drawn into the cylinder as the intake valve opens. Both systems have a throttle body to house the throttle valve, and a fuel servo/regulator to meter the correct amount of fuel and control the air to fuel mixture. The primary difference is how the fuel is metered. The RSA system (originally manufactured by Bendix Corp.) is found on Lycoming engines and is the next evolution after the pressure injection carburetor. The RSA system uses a combination of differential air pressure and differential fuel pressure to regulate and meter the fuel flow. The two sources of air are the low pressure air in the throat of the venturi and the high pressure air from the "ram air" entering the throttle body. At wide open throttle, these two forces have the greatest differential pressure, so they move a diaphragm and a valve in the fuel regulator to increase the fuel flow and pressure. The Teledyne Continental Motors fuel injection system does not use air metering force. This system relies only on differential fuel pressure.


text:
What does this indication of '10∼15 degree' that points toward the both edge of runway means?
While I study FAR AIM, 2-1-1 approach light system, I saw this indication (on the left side) that I couldn't guess what it tried to demonstrate.
It seems like runway end identifier lights, but I can't conclude since there is no explanation about it.
Does someone have a better idea, or is my guess correct?

That image is intended to describe REIL.  REIL are are two synchronized flashing lights. They can be either omnidirectional or unidirectional facing the approach area.  Unidirectional REIL are preferred.  More information is found in AC 150/5340-30.
Installation requirements are in section 7.7.5:

7.7.5  REIL.
7.7.5.1 Location.
  Locate and aim the REIL units per Figure A-79.
7.7.5.1.1 When possible, install the two light units equidistant from the runway centerline.
7.7.5.1.2 When location adjustments are necessary, the difference in the distance of the two lights to the runway centerline may not exceed
  10 ft (3 m).
7.7.5.1.3 Each light unit must be a minimum of 40 ft (12 m) from the edge of taxiways and other runways.
7.7.5.1.4 The elevation of both units must be within 3 ft (0.9 m) of a horizontal plane through the runway centerline, with the maximum
  height above ground limited to 3 ft (0.9 m) (See Figure A-93.)
7.7.5.1.5 When the centerline elevation varies, use the centerline point in line with the two units to measure the centerline elevation.
7.7.5.1.6 Orient the beam axis of an un-baffled unit 15 degrees outward from a line parallel to the runway and inclined at an angle 10 degrees above the horizontal.
7.7.5.1.7 If this standard setting is operationally objectionable, provide optical baffles (per the manufacturer's instructions) and orient the beam axis of the unit 10 degrees outward from a line parallel to the runway centerline and inclined at an angle of 3 degrees above the horizontal.

As described here, the 15 degrees is the horizontal alignment, and the 10 degrees is the elevation alignment.


text:
What is the meaning of "Steer 1-2-0" in WWII texts?
I am reading some texts about WWII and English operators tell the pilots to "Steer 1-2-0". Can anyone help with the meaning of 'steer' here? Is it a synonym of 'direction', 'heading' or 'vector'?

If you would include some context, that would be immensely helpful. What books are you reading? Can you include some quoted (and properly attributed) text with context? Of course, someone may well know based simply on what you've provided, but you'll increase your chances of a good, accurate and quick answer by providing more background. Also, take the [tour] and read the [help] - it'll only take a couple of minutes and will get you acquainted with how things work here. Welcome to [Aviation.se]!

Related

To "steer" means to change the aircraft's track (the direction of movement of the aircraft) to a certain degree in relation to the lines of meridian (north–south lines). The units are degrees from north in a clockwise direction. North is 0°, east is 90°, south is 180°, and west is 270°. Note that, due to wind forces, track is not the same as the heading (where the nose is pointing).

Looks like there's some disagreement about whether "steer 120" refers to heading or track. Do you have a source showing that it refers to track?

With just a compass and no way of determining ground track via INS or GPS, I would wager it is the heading.

Yes. 'to steer' = 'to change course to', and the number is a compass heading. Source: reading lots of books on WW2. The term is still in use on ships, not so much in aviation any more.

The modern ATC phraseology is "Fly heading 1-2-0".

Looks like there's some disagreement about whether "steer 120" refers to heading or track. Do you have a source showing that it refers to heading?


text:
Can a TCAS or Marker beacon antenna be installed inside a radome?
I was wondering how sensitive these systems are.
We are planning a modification which will involve either moving these antennas or leaving them in place under a radome (the radome is designed for x-band frequencies)

Sorry, you're thinking about modifying a safety system that you don't understand,on the basis that somebody on the internet said "Sure, go for it"? That really is staggeringly bad judgement.

Who is the "we" in your question? No need to give the specific organization; something like "xx crew at a single-runway regional airport" or "airplane xx-function team" would likely be sufficient.

You do realize that virtually all TCAS and most MB antennas come with their own 'radome'?  That's effectively what that white shell is. Also, antenna placement on an aircraft is not a random process so moving them takes careful consideration of necessary radiation patterns and potential interference. If you're planning on adding an x-band antenna that needs a large radome (that could potentially encompass the TCAS and MB) you need the assistance of a qualified RF engineer and DER, not this site.

Hi all. Thanks for your comments. David - the answer is no... We're brain storming at very early stages so I wouldn't jump to conclusions about our judgement quite yet. CVn - we're a design team in a small company looking at modifications to a business jet. Gerry - noted, thanks. Delta Lima - perfect. I was hoping to get some extra insight (I did) and maybe hear about specific cases (not yet).

Theoretically it can be done; a radome is an antenna enclosure for a radar. It is designed to have sufficient permittivity at the frequencies of interest. For TCAS, you need to look for 1030 MHz and 1090 MHz (IEEE L-Band). Marker beacons work at 75 MHz (VHF)
It is very important to make sure the TCAS antenna has good line-of-sight to all directions. If not, TCAS will be blind in some directions, with potentially dire consequences. If it is the TCAS directional receiver antenna plan to cover, you have to be very careful; near field interference can cause the directionality of the antenna to be affected, causing misleading position indications on the TCAS display.
So whilst in theory the you can put the antennas in a radome, in practice you have to very be careful and you will require many measurements to validate that the setup actually does not degrade the performance of TCAS.


text:
TCAS II - bottom omni-directional antenna
I know that the TCAS II system has a lower antenna which can be either omnidirectional or directional.
How does the functionality of the system change? If the antenna is omni then I think / assume that it cannot know the bearing of an intruding aircraft and therefore can not provide data to position it on a display. Is it only used for transmitting interrogation and/or receiving other data?
Thanks,
Ori

The directionality of a TCAS antenna is ONLY used for positioning the bogey on the TCAS display, it is NOT used for determining time-to-contact. So you're still going to get TAs and RAs from the Omni antenna even if the upper antenna is blanked, but you won't get the display of that traffic.

Thanks for your answer. My question is what would happen if the lower (omni) antenna is partially obstructed. The upper (directional) antenna is not obstructed.


text:
What does the NetJets "QS" stand for?
Every NetJets aircraft that I've seen has a tail number ending in QS. Knowing aircraft operators, I'm sure it stands for something, but I don't know what.
What does the QS stand for in NetJets tail numbers?

The "QS" first stood for quarter share, according to the 1998 issue of Flying. Each aircraft will have multiple owners to help bring the cost down for the owner.

This directly contradicts the other answer, which is backed up by a source.

This is actually what I have always heard too, and have heard from many other pilots.  Perhaps there are two meanings, or perhaps the pilot community has come up with it themselves, but it is a commonly known "meaning" for it.

Or perhaps it had this meaning first and the other one was created later by the marketing team. :)

Turns out it did!  Knowing what to search for, I was able to find an earlier source.

In the United States, tail numbers can be arbitrarily assigned, assuming it is available and formatted per FAA requirements.
NetJets uses QS to identify their planes. According to an article in the May 2002 issue of Flying magazine, "QS represents Quality Service," (page 82).

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
To what extent are (non-urgent) PIREPs used by meteorologists?
It's inevitable. At some point during your weather briefing, some underpaid, underappreciated briefer will say "Pilot reports are requested." and you'll say "Certainly, my good sir or madam! Why, the only thing that gets me out of bed in the morning is the chance to help my fellow aviators!" and then you won't make one.
But let's say that you do make a non-urgent pilot report.  Briefers will give that information to pilots, but what about the meteorologists who actually make the forecasts?  Supposedly, they're interested in the information as well...

"NBAA is excited about the new electronic submission form that should streamline the PIREP process, and allow the information to get to the FAA air traffic controllers and the NWS Aviation Weather Center (AWC) forecasters sooner," noted John Kosak, program manager, weather, NBAA Air Traffic Services.  [1]

but what are they used for once they're submitted?

Related: Do You PIREP? Here’s Why You Should. PIREPs are used to validate high altitude weather forecasts.

PIREPs explain localized weather phenomena, typically along a path at a specific altitude in a specific location. Weather forecasters don't work that localized. They won't issue a forecast with "light to moderate turbulence experienced between 5000 and 7000 over the GRB VOR". They use weather balloons, radar, and other instrumentation to make the area forecasts. So while not an answer, I don't believe meteorologists use PIREPs at all, at least currently.

@RonBeyer -- my understanding is the primary use of PIREPs is to validate or refute forecasts -- hard to know if you got it right if you have no observations telling you what's actually up there!

This NOAA newsletter lists a number of specific ways that PIREPs are used by meteorologists:

To "assess the strength and position of the jet stream"
For thunderstorm and snow level forecasting
For forecast discussions of regional weather phenomena, like "downslope wind storms in the lee of the Sierra Nevada"
To "determine the likelihood of clouds thinning or burning off"

Their summary is:

Better reports and observations, not only from PIREPS but also storm
  spotters, Webcams and road weather networks help improve the picture
  of what’s going on in the atmosphere. Automated temperature, wind and
  humidity reports from MDCRS and the Aircraft Communications Addressing
  and Reporting System in commercial aircraft also get incorporated into computer models. All of these observations lead to improved forecasts and warnings.

There are a few very generic references out there too. A 2014 edition of FAA Safety Briefing says:

The information will then be added to the distribution system to brief
  other pilots, help generate inflight advisories like AIRMETs and
  SIGMETs, as well as updates to the Current and Forecast Icing Products
  (CIP/FIP), and improve overall forecast accuracy.

And an AOPA article has a brief mention:

when the Aviation Weather Center (AWC) receives a pirep,
  meteorologists use it to verify that their weather forecast is correct
  or amend it if the pirep contradicts the forecast.

Finally, PIREPs (and AIREPs) are shown on the NOAA website, although that probably isn't what you had in mind by meteorologists 'using' the information.


text:
Can I fly a SID/STAR if a navaid is NOTAMed inoperative, using RNAV?
Take a SID like this, BARPI2K at LJPZ.

The textual Route description says

BARPI TWO KILO
Climb on track 315 to 1700 ft; LT to PZ L; overhead PZ L; LT on HDG 295; intercept PZ QDR 325 PZ L to BARPI. Cross PZ L at 3400 ft or above.

Now the navigator in my aircraft can load and fly this procedure perfectly based on GPS along, without ever referring to the ADF which is only installed in the aircraft for compliance reasons.
But what if the PZ locator is NOTAM-ed out of service? Can ATC still assign this SID?
I'm torn on this as on one hand it is a navaid that is part of the procedure, but on the other hand this is is an RNAV SID anyway (it ends at a fix) so they know I'm still capable of navigating to "PZ L" with the exact same accuracy as before.
Approaches are another, much clearer matter, but I could not find anything official on SIDs/STARs.
This example is EASA (Slovenia) by the way, but of course we can discuss national differences if there are any.

This is legal in the United States, per AC 90-108. GPS can be used in lieu of NDB or DME in most cases. One of the exceptions is when the procedure is NOTAMed as not authorized. But this applies to the procedure as a whole- if just the navaid is NOTAMed out of service using GPS is still permitted.
A similar idea seems to have been adopted by EASA recently, as seen in this amendment document:

Applications of RNAV substitution include use to [...] navigate to or from a VOR, or NDB, except as lateral guidance in the FAS of an IAP

and

RNAV substitution for ADF, marker and VOR may be used where airborne and/or ground-based
equipment is not available

So, if my reading is correct, this was illegal until very recently but might be legal now. It would be wise to check with someone more familiar with Slovenian law in particular, though.

That's really interesting, the amendment you linked to is very explicit on the matter, but also as you note it's very recent, good to know. Thank you!


text:
Why don't short runways use (downhill) ramps for takeoff?
This is a followup on question: Why don't short runways use ramps for takeoff?
There are multiple answers to that question that answer why an uphill ramp at the end of the runway does not make sense. But what about going the other way?

I would imagine a downhill ramp at the beginning of the takeoff roll could give the aircraft more energy on takeoff (converting potential energy to speed), and that could indeed improve takeoff performance. This would be useful at places where extending the runway is not possible.
How the aircraft would get up there is another question, but worst case scenario it could always back-taxi on the runway before turning around and taking off.
Is this practice ever used? If not, what are the reasons?

Back-taxi up the hill, turnaround at the top to come down? Sure, that is done at places where the terrain requires that. Jaffrey, NH comes to mind.

There are a number of strips around the U.S. that are uphill-downhill strips. Near us is McKenzie Bridge State Airport in Oregon. You takeoff to the west, land to the east, regardless of the wind. There have been fatal accidents involving pilots that ignored that, choosing to operate into the wind.

Can you elaborate on why you think this would be different? Most of the issues mentioned on the other question would still apply here, as if you switch directions to follow the wind, now the ramp is at the departure end again.

At least one does...

With the sloped end(s) of the runway, the requirement for 35' clearance on takeoff/go around becomes a limiting factor to overcome. This idea reminds me of the dented sterns on carriers used for carrier quals with first time students. getting below the threshold is not a good thing on short final.

@Dave At least two! https://en.wikipedia.org/wiki/Tenzing-Hillary_Airport

Many of the arguments against using a ramp from the other question is valid for this as well. Any ramp means a height difference between the ramp itself and the runway, for it to actually make a big difference I suspect a fairly long slope from the ramp to the runway is needed, and this will obstruct the runway for landing aircraft. If the ramp is above ground, aircraft taxiing for take-off would also have to overcome the upward slope, meaning that more fuel is needed for taxi.
You'd also need a ramp at the opposite end; the runway would basically look like a stretched out 'U'. A possibly unintended consequence of this is that the aircraft would at some point reach the point where the runway begins to slope upwards again, resulting in the aircraft either having to abort or use additional power to get airborne.
To avoid such a case you would have to stretch out the runway so this isn't an issue, and if the goal is to reduce the runway length the current design is more efficient. Alternatively you could create a separate runway for each direction, but then you'd be faced with potential crashes whenever a pilot tries to land in the wrong direction. This would also result in difficulties for airports located in built-up areas where there simply isn't available room for additional airport infrastructure.
If you keep the ramps on ground level and the runway center below you'd also need working drainage pumps whenever it rains or snows. If not, the runway would quickly be reduced to a pond with very wide roads leading into it. Depending on where in the world you are, water might seep in from the surrounding terrain as well, making reliable drainage even more important. This is generally avoided by building runways with a slightly raised centerline so that water runs out to the sides so that you can use "passive" drainage systems such as pipes, ditches, pools etc where no machinery is required.
There are some airports such as Lukla where one end of the runway is substantially higher than the other, but due to surrounding terrain it is only possible to land and take-off from opposite directions. Landing aircraft can use the upward slope for an additional braking effect, while aircraft taking off will get a speed boost from the downward slope.

I'm picturing some kind of hydraulic lift used to raise and lower the ramp at each end so that it can be reconfigured depending on the wind...  ;-)

Well, but then you end up adding a lot of complex machinery which would cost a lot of money to maintain and operate, just to save a bit on the take off distance. The runway, ramp and slope would still have to be adapted to the largest aircraft you would expect, meaning that smaller aircraft might not even need the ramp at all. According to https://community.infiniteflight.com/t/list-of-aircraft-runway-requirements/107832 a fairly common regional jet requires a runway of around 3500 ft while a 747 needs up to 7000.

@bjelleklang, I think Lnafziger was being somewhat sarcastic.... (I know, it's hard to tell over the internet)

Surely you could provide for passive drainage on a sloped-at-both-ends (lengthwise) runway. I can't imagine that part being much more difficult than for a normal/flat runway. Snow is going to be a problem no matter how you do it, because as long as the temperature remains below freezing it has a tendency to remain where it falls (unless whatever it lands on has a very strong slope; enough so that it would likely make the surface useless as a runway) but that doesn't seem to be more a problem in the case of what OP proposes than for a normal runway.

It depends on how it is constructed. If the ends/ramps of the runway are above surface the center would be closer to the surface, and that would make it easier. If the center is 10 meters below the surrounding surface passive draining would be more difficult, and draining in general would be much more important.

it could always back-taxi on the runway before turning around and taking off.

So ... that would limit the steepness of the slope significantly, and thus the potential benefit.
Most other aspects are already covered by Bjelleklang's answer: Landing aircraft would either have to clear the obstacle before being able to touch down, or, on days when the wind blows the other way, they'd fall over the edge if they don't brake in time (rather than, as these days, get stuck in the grass behind the runway end)

A "relaxed definition" of this  concept is in use today on aircraft carriers.
Notice the ramp in question is essentially a mechanical device to increase the total thrust force on the aircraft, which increases acceleration.  This is also exactly the same as pitching an airborne aircraft down, or launching a model aircraft by throwing it.  RATO can help too.
The energy input for higher rate of acceleration:  F = ma total = ma thrust + ma gravity, steam catapult, thrown with hand etc.
The result is higher air speed for a given distance as compared with no "ramp".
The practicality of building such a device would be questioned.
Generally, it's landing distance that is limiting.
But many soaring birds take it one step further, they simply jump off a cliff (disclaimer: attempting without certified wings may be hazardous to your health).

Here's an example of a sloped up runway, midway down looking southwest. The end is definitely sloped up.  We're typically off the ground well before that tho, the runway is 3110 feet long.
Taking off from that end towards the northeast, going downhill to start will help with the takeoff acceleration.

I'm not sure this anecdotal reference actually answers anything...

Other than being able to takeoff aircraft may have to stop after the start of takeoff run. If the slope is sufficiently steep how would you propose to stop the plane within the remaining runway?


text:
What military aeroplane seen at Prestwick is this?
I saw this plane flying out from Prestwick airport yesterday but what is it?

Based on the fact that this looks like a 4-engined jet, with a T-tail, and winglets. I think it is a C-17.

(wikimedia.org)

Number of Küchemann bodies also matches, and the ramp might be identifiable as well. Looks like the correct answer.

It's also got the landing gear in fairings under the fuselage, which is a common setup for military transports (to keep the inside load space wide for the full length).  A little sub-fin also helps agreement with this type.

C-17's fly in and out of Prestwick regularly. Prestwick has the longest commercial runway in Scotland (Macrihanish is longer) so it's a useful facility for exceedingly large cargo aircraft.

And the C-17 is the only four-engined jet cargo aircraft flown by the RAF. (Of course, we don't know from the picture that this is an RAF plane.)

It's a C17.

RCH560 C17 08-8193 arrived off the ocean about 0225L

As taken from this forum

Good find! RCH has the callsign Reach and is commonly used for USAF C-17 flights.


text:
How much does an air data module cost?
Curious how much Air Data Module and Angle of attack sensor costs, such that is used on commercial airliners.

I don't know specifically what that one costs, but as a "civilian" they will be extremely difficult to buy. I work with a company that manufactures avionics and sensors like that, and some of those types of sensors exceed $50,000.

You can't really estimate the price because each commercial airliner has a different design and manufacturers have contracts with suppliers. Your best estimation is by looking at the cost as a spare part

Thank you. I'm not looking to purchase one. I'm looking into manufacturing them and trying to estimate the market.
Commercial airliners have different designs, however Honeywell, for example, has a list of standard equipment. It is not custom made for each airplane.
https://aerospace.honeywell.com/en/products/navigation-and-sensors/air-data-modules
Alas they don't have an online store. For spare part I could only find used equipment.

@SlavkaStack Each airframer orders customizations particularly in software, outputs, wiring, and mounting, even though the base module is the same. If you're trying to make your own, Airbus and Boeing will never buy from you; they buy complete integrated suites from Honeywell, Rockwell and Thales. They also need 30+ years of availability and the possible liability if it malfunctions and a 300 person plane crashes. Your best bet is to look at the ones from small prop planes.

You don't have just a module receiving AOA on an airliner.  You have an Air Data Computer that performs numerous functions with AOA just one of many inputs. Pricing depends on who's buying.  An OEM purchasing ADCs in bulk might pay 100k per unit.  An airline or other 3rd party might pay 150-200k for the same unit as a spare.  For the vane, the spares price might be 30k, while the OEM pays 10-15k.  OEMs know they have a captive market with their airline customers and they know the costs are just passed on, so the price gouging is quite brazen.

@user71659 Yeah, I realize it is a difficult task, but I think I have a better idea for AoA than existing vane or Pitot based systems, so I'm going to try.

@JohnK thank you, that is very helpful

For airliners, a lot of money, in the tens of thousands or more. Thales Aerospace is one of the manufacturers of AOA's for transport and military aircraft -- the word "cheap" does not exist in their vocabulary and "inexpensive" is a matter of opinion. For GA aircraft they are significantly less expensive, about US\$2000 or less. For aircraft with other than standard airworthiness certificates (experimental, homebuilt, etc.) the cost falls well under US\$1000. Sometimes manufacturers don't call them AOA's, and instead refer to them as "Lift Reserve System." For a general idea of the cost of GA AOA systems, check Aircraft Spruce and search for "AOA".


text:
Difference between general, airframe and power plant concentration courses
Trying to enrol for an aircraft maintenance technician course but the options are three that’s general, airframe and powerplant concentration. With the general being an affordable course to pursue, will it be advisable if I choose that than airframe or powerplant and would it be enough to prepare me for FAA exams ?

Are you sure it's 3 separate courses and not just two? "Airframe and powerplant" is the FAA certification. General may not require an FAA exam.

Closely related:  https://aviation.stackexchange.com/q/62311/167

The US Mechanic certification has two components, Airframe and Powerplant. The license is generally known as an "A&P" license because most candidates choose both. There are, however, three exams. The third is the General knowledge exam. You have three choices for licensing:

Airframe only
Powerplant only
Airframe & Powerplant

For all three options, you must take the General exam as well. Taking a general course will only prepare you for that exam, which does not lead to any license or certification.


text:
Second career as an avionics technician
I will soon be retiring from my first career as an electrician on large construction projects. Planning on becoming an active private pilot again and I am
basically an aviation nut. I am curious as to what certifications are needed to be employable at an avionics shop ? What would be the best/quickest route to get there?

I think it may help to clarify if you want to work in an avionics backshop performing component level repairs or performing avionics line maintenance. The two are quite different and require different levels of certification. The term “avionics shop” could be confused for either in the industry.

Good points, @Frank. I assumed line maintenance because the OP said he worked as an electrician, and not a component-level repair tech.

This answer assumes you live in the United States. You should consider attending a Part 147 program at an Aviation Maintenance Technician School approved by the FAA. Some avionics technicians also get themselves an Airframe mechanic's rating from the FAA because a good percentage of what a line avionics technician does has to do with components of the airframe. (As a side note, military experience as a line avionics tech is considered sufficient to qualify to take the tests for the Airframe mechanic rating). You can also become certified through a repair station, but that may only qualify you to perform specific work. You should definitely also get the FCC radio-telephone operator certification or Aircraft Electronics Technician (AET) certification from the National Center for Aerospace and Transportation Technologies.


text:
Is it possible for a person to fly with mechanical wings attached to his torso?
I’ve seen several adaptations of this concept in fiction from the tales of Icarus to Falcon in the MCU. But is it possible in reality for an average human to be able to fly through the air by wearing these gadgets?
If it is possible, then how would this work?

People are flying with wing suits only. You might want to specify what exactly you mean with flying.

what do you mean by mechanical wings? And are engines allowed?

I assume you mean sustained level flight, with no motors or engine assisted thrust -- only thrust through human powered flight? Perhaps you could update your question to include this, if this is right.

Does Yves Rossi's suit count?

Flagged as unclear. Plane wings are a thing. Flapping wings another. Rockets with wings like Falcon again another. What is the question here?

You could reasonably call a hang glider "wings strapped to the torso" for this purpose -- hence the answer is "yes, sort of."  With a well designed glider, one can launch from sloping ground and soar on slope lift or thermals, limited by oxygen requirements and fatigue.  Hang gliders have done cross country flights running to many hours, stayed up literally dawn to dusk on ridge lift, and flown high enough for the pilot to require oxygen (and then some, I believe the altitude record is around 18,000 feet).
None of this, of course, is powered by the pilot, using either arms or legs, but this is clearly "wings strapped to the torso."
Add a small engine and you get a modern ultralight/microlight, or something like Rocketman's jet powered wings.  The latter, especially, is still pretty clearly "wings strapped to the torso."

Humans aren't strong enough to fly using their arms to flap a wing.

According to Usherwood, for a human to take flight on flapping wings, “your body would have to be made almost entirely of muscle.” In other words, humans make terrible hummingbirds.

You can build an ultralight aircraft that's pedal-powered (human leg muscles are much stronger had have better endurance than arms), but this is still on the edge of human capability. These aircraft will fly low and slowly, and the distance record is ~115 km.
Add an engine (or glide from high altitude), and it becomes feasible to use a wingsuit (or a rigid wing attached to a harness).

I'd like to see a reference for the statement that a human's arms aren't strong enough to fly at all. It seems at least plausible that if the legs are strong enough to fly for ~115 km using an ultralight concept, then perhaps the arms can be trained to be strong enough too. I've never heard of this though, but it seems plausible, hence the need for a citation in my opinion.

@AlphaCentauri Measure around the biceps/triceps of your arm, then around the triceps/quads of your thigh.  The muscle power available in each case is approximately proportional to the square of the circumference; in most people with athletic build, that'll be between four and eight times the power from the legs as compared to the arms, and it takes a pretty optimized design to simply lift off by pedal power.  Yes, pectorals and deltoids might add, depending on wing design -- but legs are evolved for walking and running; arms are not.

@AlphaCentauri, one only needs to compare the relative size of a bird's breast muscle in relation to the rest of it's body, to the ratio of the human pectoral muscle to the human body to understand that we simply don't have the muscle mass where it is needed to have enough power to sustain flight.

...or as hrobeers notes in his answer, try to do an iron cross, or even just see how long you can sustain a wide push up position simulating a glide.  Or "flap" by doing pushups and see how long you last.  (in reality push ups are much easier that supporting your weight with arms fully extended)  No citation needed when you have personal experience to guide your perspective!

@AlphaCentauri Hobbes is referring to the Daedalus project which used trained, professional cyclists. Not your average human, in other words. I tried the Daedalus simulator once and was able to take off for a short hop but was exhausted within a few minutes.

@ZeissIkon The limit is not how many muscles you can engage but how much muscle energy is supported by your respiratory capabilities and your blood circulation. For a short term you can rely on burning ATP, but that won't last very long.

@AlphaCentauri: There's a major difference between human-powered flight using propellors, and flight using flapping wings.  I wouldn't be surprised if a trained handcyclist could get aloft in a modified Daedalus plane, but I don't think anyone has managed to build a successful human-carrying ornithopter.

Assuming you mean wings attached to one's arms:
Only trained gymnasts are capable of holding the Iron Cross for a short period of time (see Rings_(gymnastics)).
With the Iron Cross, the center of force counteracting gravitational acceleration is one arm length away from the center of mass.
Depending on the aspect ratio of the wings attached to one's arms, it'll be harder or lighter to hold your wing compared to the Iron Cross, for non-vertically accelerated flight. (ref. Force_and_levers)
Therefore you only see wing-suits with very low aspect ratio wings in use.

You didn't specify whether engines were allowed, but Jetman:
https://www.youtube.com/results?search_query=jetman


text:
Why does aircraft stability increase when it transitions from subsonic to supersonic flight?
I am puzzled why would the aircraft be more stable at high speed flight at high altitudes. Given that the Centre or Pressure moves gradually towards the 50% MAC region, once past Mcrit.
Has this got to do with moments and the neutral point?

Static longitudinal stability (also called static margin) is determined by the distance between the center of gravity and the neutral point¹. The neutral point is at a quarter of the chord at subsonic speed and moves back to half chord once the aircraft flies fully supersonically. This means that the static margin will greatly increase when moving from sub- to supersonic flight.
In order to keep the center of pressure at the center of gravity, in supersonic flight the elevator needs to create lots of downforce. The bigger the difference in lift per area between wing and elevator, the stronger pitch stability will become.
This effect makes the transition between both regimes tricky: When accelerating, aircraft experience the shift in the center of pressure as Mach tuck, and when the trim facilities are not sufficient, the aircraft might enter an uncontrollable dive.
In the reverse direction, an aircraft trimmed for supersonic flight will experience a pitch-up moment from the forward shift in the center of pressure once it slows down, which can stall it or overload the structure.
¹ I could also talk of the center of pressure here, but that would be less precise. The neutral point is the center of pressure for all angle-of-attack-dependent lift forces, and it is those which determine pitch stability.

Thank you for the response Peter, however wouldn’t keeping CP and CG result in a very unstable aircraft? I mean, isn’t it better for your CP to be aft of the CG so that the aircraft experiences a natural nose-down moment?

@shogunnyan: Any difference in the location between CP and CG will let the aircraft rotate. The aircraft is trimmed precisely to move the CP exactly below or above the CG.

i see! Ok! I understand now! Appreciate it Peter!

The CP of the wing will, for most airplanes, still lie aft of the CG which is usually required to be longitudinally stable.
Peter was addressing the whole airplane.
The CP of the airplane as a whole (Lift, Weight, Drag, Thrust), will need to lie exactly in the CG or a moment will exist and rotation will take place.
Peter chose to use the CP of the wing and the tail together, the total CP.
(which indeed needs to be in the CG or pitch change will occur)


text:
Why does the 737NG EGT drop during take-off?
I noticed that the EGT drops a bit when I hit TO/GA for take-off on a 737-800.

I think you may add some context (it may depend on ambient pressure and temperature)

@ManuH Seems like a perfectly valid question to me.

@J.hougaard I agree. Adding context will bring this question from valid to well documented.

Is this observed in the aircraft, the simulator, or in a program on a computer?


text:
How to use wind currents for constant elevation in gliding?
I am using X-Plane learning some basics in aviation. Currently, I'm using the glider so I can focus on flying and not engines.
I've heard of gliders being able to catch drafts so as to keep continuous flight. Is there a rule to be able to do this? I thought by riding with the wind and occasionally intersecting I might keep up the energy, but it does not seem to work that way.

This is going to depend on whether and how accurately your simulator simulates thermals, ridge lift, &c.  It can be done in real life.  Maybe you should start with a good book on the basics of soaring?

Gliders do NOT rely on (horizontal) wind to stay airborne. You want to read up on adiabatic processes and thermals instead. As for focusing on flying and not engines, sure you do not have to learn about engines to fly gliders, but what you save on theory about engines you will have to make up for in theory about meteorology. Make no mistake, flying gliders is a complicated topic.

You need some inhomogeneity to extract energy. For gliders there are three basic ways to do that:

Thermals: The sun heats up the ground which in turn heats up the air above it. Hotter air is lighter and rises up. It keeps rising as long as the lapse rate of the atmosphere is above the adiabatic rate. This means that three conditions must be met for thermals to occur:
1.1 Sunshine
1.2 Sufficient atmospheric lability
1.3 Ground that easily heats up, such as forest or sand.
Ridge lift: Air streams across a hill and rises up on the windward side. Behind mountain ranges you might also find lee waves, an atmospheric oscillation caused by wind blowing across a mountain.
Dynamic soaring: Here the wind gradient in the atmospheric boundary layer is exploited by flying turns while pulling up when turning into a headwind and diving down when turning into a tailwind. This is currently only used by Albatrosses and has been experimented with by Ingo Renner, but is much too stressful for human pilots if done for extended periods.

Look at the variometer in your glider and try to fly circles when you see an indication of rising air. Tighten the circle when climb rate decreases and flatten it when it increases in order to center the glider in the thermal.

By 'lee wave', do you mean gravity wave (a.k.a. mountain wave) as seen here:  https://www.youtube.com/watch?v=yXnkzeCU3bE which gives you terrifc lift but also very dangerous downdraft?  There is also lift from 'convergence' where two winds meet, typically a sea breeze bumping up against the met wind: https://en.wikipedia.org/wiki/Convergence_zone.  I doubt any desktop flight sim will simulate these

@DaveGremlin: I never heard the term gravity wave for lee waves, but yes, mountain wave is another word for lee wave. Wikipedia uses this term, so I used it here, too, since I linked to the Wikipedia article. Convergence zones give too little vertical speed; I have never heard that they can be used for gliding.

@DaveGremlin. "gravity wave" just means one of the restoring forces driving the oscillation is gravity, and that is true of most transverse waves in fluids and on fluid surfaces, so e.g. waves on water are also "gravity waves". In contrast "lee wave" indicates the wave is formed on the lee, downwind, side of an obstacle due to the obstacle disturbing the flow, so it is a more specific term here.

Gliders do not fly with a constant elevation, the goal with gliding is to find updrafts and ride them as high as possible, then trading altitude for distance until another updraft can be found. So the flight profile of a glider goes up and down, it does not stay constant.
Simulators are good for learning processes but not so good for learning the aspects of flying that require more feel, and gliding is definitely a feel thing. Glider pilots learn to recognize where thermals are active and ride them up, not something you'll get in x-plane or any other simulator I've tried. I would suggest powered flight as it's more realistic and you'll learn more.


text:
Why does the low voltage warning light not illuminate when the alt switch is on, but the engine is off?
As part of the pre-flight inspection, one of the checks is to verify that the low voltage light is illuminated when switching just the battery on. This makes sense; there's a low voltage and the battery is being discharged because we're running everything off the battery, and the alternator is not providing any power.
However, as part of the startup - just before ignition - we switch both the battery and alternator switches on. At this point, the low voltage light is not illuminated, despite the alternator not providing power as the engine is not running. This doesn't make sense to me - though we've turned the ACU on, the alternator is not providing power. This seems like something that should trigger the warning light.
I've examined the C152 POH and it shows a basic electrical layout. I'm not sure as to the copyright of the handbook, so I won't post it here. It is available online for those interested, figure 7.7. Unfortunately, this did not help explain the behaviour I'm seeing.
I've reproduced this on two different 152s. Why does the warning light not detect the fact that the alternator is providing no power, or am I completely misunderstanding the function of this light?

C152 models until 1978 had a voltage regulator, an over-voltage sensor, and an over-voltage indicator light. See Carlo's answer for the wiring diagram.
Starting from 1979, Cessna used an Alternator Control Unit (ACU) (Cessna Service News, 1978). This ACU integrates the regulator, as well as over- and low-voltage sensors. There is no over-voltage indicator any more. Instead, the ACU automatically reduces the alternator field voltage when over-voltage is sensed. This is the new (as of 1979) wiring diagram:

Image source: Flight Literacy
The low-voltage warning light is directly connected to the ACU. Unfortunately it is not easy to find a schematic of what is inside the ACU, and it appears as black box to me.
The expected behavior of the low-voltage warning light is to indicate whenever the alternator does not provide power, but the battery does. It is normal behavior if the low-voltage warning light comes on when the engine is idling, since the alternator does not provide sufficient power at low rpm.
I read somewhere that the low-voltage sensor in this ACU simply compares the voltage (on the primary bus) with a fixed threshold. [will add the source if I can find it again]. It is not able to directly sense if the power comes from the alternator or the battery. Instead, it relies on the fact the alternator needs to supply about 4 V above the battery voltage to charge the batteries.
You tried but could not see the low-voltage light when both sides of the master switch are on, and the engine is not started. You tried on several C152 to make sure your first plane is not behaving abnormal.
My best guess is that all the planes you have tried had healthy and fully charged batteries. The voltage levels were always above the trigger threshold of the low-voltage sensor.
You could try to switch on as much electric load as possible and see if the warning light comes on, immediately or after some time of discharge. If you have the possibility, you could measure the bus voltage.
A full 24 V battery without load would show about 25.4 V (or higher for AGM or gel types), and I believe that is above the threshold for the low-voltage sensor.

This definitely seems to be a likely contender for the explanation - I'll give it a go on my next flight. Hopefully I'll be in a plane that's been sitting around for a bit and isn't fully charged. Thanks!

Thinking about this for a bit - if the batteries were fully charged and healthy and were providing voltage higher than the threshold, then I'd expect the light not to turn on even when just the battery switch was on. So there's clearly something going on with the ACU, but I'll test leaving both switches on and applying a load for a while next time anyway

In the case of BAT=on and ALT=off, the ACU is not powered and the ACU somehow pulls the low-voltage light is pulled to ground. The other end of the low-voltage light is connected to the primary bus, that is connected to the battery. This is an intended feature to allow testing the light.

I've ended up doing a bunch of research around alternators and regulators (the majority being in cars, but the idea should be approximately the same). The flaw in my thinking was assuming that the sense wires were responsible for controlling the light. Turns out, those inputs are used to regulate the field over the alternator. With that in mind, it's highly likely that the power in line is used to control the light. When the ACU is unpowered, you rightly stated the light is pulled to ground (and thus turns on). When the ACU is powered on it's supplying the battery level via 'Power in' (cont)

And that is the voltage used for the measurement to either balance the voltage across the light, or to drop it enough to illuminate. Again, you're right that draining the battery should switch the light on with the ACU unpowered. Also, it seems that the alternator is only being indirectly checked for proper function - if the load is low enough, a faulty alternator may not trigger the light until the battery discharges enough. I suppose that should have been obvious to me given it's a low voltage warning, and not a faulty alternator warning :) Thank you for pointing me in the right direction!

If the ALT switch is not closed, but the BATT switch is closed, battery power is allowed to flow through the ALT FIELD breaker, through the Over Voltage warning light, and grounds through the Over Voltage Sensor.  If both the BATT and ALT switches are closed, current flows through both the ALT switch and maintains battery voltage at both terminals of the Over voltage warning light which prevents it from illuminating.  This design feature allows the Over voltage warning light to illuminate when either the alternator is not connected to the main electrical bus or the alternator is malfunctioning.

The electrical layout here is a little different from what I've seen. Here's what I saw at my training and found online: https://i.sstatic.net/5gI34.png . Your picture makes it a bit clearer as to what's happening. However, looking at your diagram, it looks as though if the wire between the alternator and the main bus (joining just next to the ALT CB) was severed, the light still would not illuminate as the voltages are balanced. In fact, that appears to be the case even if the entire alternator was removed, so long as the regulator was still grounded. Could you expand on this?

Well this is the schematic versus the actual wiring of the electrical system on the airplane. However your point does raise some merits. What would be required is the severing of the wire between the battery and the alternator breaker.  This, or, effectively, simply switching off the BATT switch, would extinguish the Over voltage warning light, regardless of the position of the ALT switch.

That’s going to depend on the year that that airplane was built, is that varies. I would also have to see the specific POH for the airplane Rob is flying to see exactly what system is installed on it. The principal remains about the same.

Good day!
A week ago i was fixing the same problem. The owner of regulator stated that there is no warning light for LOW VOLT, when Master BAT is switched ON and Master ALT is OFF.
I had opened regulator and checked schematic on PCB, and now hope that i understand how it works.
Current flows through LED only if ALT voltage becomes lower than BAT voltage, and this difference becomes equal to forward voltage drop of LED used in LOW VOLT indicator of your airplane minus about 0,6 volts (drop on diode D1). In my case there is used more or less standard RED color LED with forward drop of approximately 1.8 Volts with current of 5 mA through it. This means that if voltage of Alternator becomes less than voltage of Battery for 1.8-0.6 = 1.2 Volts or more, LED will open and red light appear on the instrument panel.
On the pictures you can see schematic of this. Please note, that this is simplified schematic, which i created in simulator in order to explain the principle of how is LOW VOLT indicator working. Red LED shows light and indicates, that voltage of Alternator is lower than voltage of Battery.
On the 1st picture there is situation when Alt voltage 26V is higher than Bat voltage 24V, and LED is not opened (no red light).
On the 2nd picture Alt voltage becomes 22 Volts (less than Bat voltage for 2 Volts), LED is opened and red light appears.
And on the 3rd picture Only Master BAT is switched ON, but Master ALT is switched OFF, so voltage from ALT can not close or open LED, current flows through LED and resistor R2, and red light shows LOW VOLT.
The owner of regulator tried to connect simple lamp instead of LED, and of course normal lamp did not show any light with only 5 mA current. After he replaced lamp with LED, everything works correctly.


text:
Why not make the touchdown zone of runways wider than the rest?
Reasons:

Save money by making the rest of the runway narrower
Larger margin of error left and right
Easier to turn around, if necessary

And if the reason that it isn't done is merely for regulation/legal reasons: Is this something that would be practical if it were allowed?

It sounds like the underlying assumption is that it is easier to stay centered after touchdown. I think that might not be true, crosswind and e.g. uneven braking power can be problematic even after the wheels are already on the ground.

Consider the same question phrased a different way could we make some parts of the runway narrower than the rest?, and you'll probably come up with quite a few counter-arguments.

How would it give you a larger margin of error? It's no use having a wide touchdown zone if you're then going to go off the runway as it narrows.

@dtgq What problem are you trying to solve? Planes running off runways is pretty rare.

@DanHulme: Presumably because if you touch down on the runway, but off-center, you can easily steer back to the centerline without breaking anything, whereas, if you touch down off the side of the runway, there's a good chance of getting your landing gear ripped off (especially if it's just rained and the adjacent ground is soft and muddy), ingesting debris into your engines (requiring at the very least a new fan, and probably new compressor stages and a new combustor as well), or something else bad happening to your plane (not to mention all the passengers whose trips you've just ruined).

"if you touch down off the side of the runway" then you've screwed up badly and should have gone around.

You'd be screwed when the runway turns around and operates in the other direction!   :)

Because most runways already are as narrow as safely feasible.
Let us look at your question piece by piece:

Save money by making the rest of the runway narrower

You seem to be assuming we are currently deliberately wasting asphalt on making runways wider than needed, and could build them narrower. As they say on Wikipedia: [citation needed].

Larger margin of error left and right

The touchdown zone is the whole runway, as long as the aircraft in question can stop afterwards, so if you start down this alley you'll find it cheaper to complete the runway in the same width.

Easier to turn around, if necessary

This is already done by including turn pads, on top of the nominal width. For an example, see: OGZ

Because planes that landed towards the edge of the touch-down zone would run off the side of the runway when it narrowed.

That's (one of the reasons) why we have rudders and tillers - so that planes touching down off-center can be steered back to the centerline.

@Sean and those aren't too effective until speed drops significantly for ground handling.

@Sean To provide enough time to slow so you can steer back safely, you'd probably need half the runway to be full-width and the second half could be tapered off. But that second half is the first half of the opposite-direction runway, so it has to be full-width too.

@jwenting: The tiller isn't too effective until speed drops significantly.  The rudder is very effective indeed at high speed, and its effectiveness decreases as the aircraft slows down.

At least a few runways are divided by length.  For example, once at Boeing Field (BFI) four general aviation light aircraft were cleared to land approximately at once on two runways.  My VFR landing clearance was to land in the first half of runway 14R while another aircraft above and slightly ahead of me had to stay at 500 AGL(? I forget the exact number) until the threshold and then land on the second half.  The left runway had something similar occurring at about the same time.
Having irregular width runways doesn't help this much.  Also it is difficult to imagine that the non-ends would be graded any differently.  In the overall project of constructing a runway, it is highly likely that the land preparation, utilities, and grading are like 80% of the cost of the surface.  A forum exchange breakdown of a Canadian 7000 x 100 foot runway is:
$   250,000   geotechnical analysis
$ 4,000,000   gravel (60 cm of 7.5 cm minus, 25 cm 1 cm minus)
$ 2,500,000   labor and equipment rental
$   100,000   quality testing (compaction, etc.)
$ 2,000,000   asphalt (15 cm)
$   200,000   lighting
$    10,000   painted markings
 ----------
$ 9,060,000   total

Would making the shape narrower increase any of those costs?  Probably.  Certainly less materials should decrease the overall cost, and maybe labor could be economized.
For strong crosswind landings, I usually use all of whatever width there is!

Interesting mixture of units.  Runway area in feet and depth in centimetres :-)

@uɐɪ So volume is in square feet centimetres!

Similar thing happens at Oshkosh every year, right?


text:
Is it possible to eliminate induced drag completely?
According to Wikipedia an airfoil of infinite length would create zero induced drag. Therefore, would it be possible to make a wing that creates no drag if you ignore viscous effects (skin friction) by walling it off on the wingtips to prevent vortex formation? Or is there another drag creating mechanism?

Well, how do you wall it off completely without involving infinity? With infinity long wing you are already walling it off although the wall is horizontal.

But to directly answer your question: yes, you just don't try to generate any lift then your induced drag will disappear.

@user3528438: Or use a blimp, or a jumpjet...

The infinite span has nothing at all to do with having no ends.
The ratio of lift to induced drag increases with span. If you fix the lift, and vary span, the induced drag will tend to zero as the span tends to infinity. That means in limit a wing of infinite span generating finite lift (and therefore flying at zero coefficient of lift!) will have zero induced drag.
This is a highly abstract approach to things and I don't think it provides any useful insight.
Anyway, forget about the vortices. They only happen behind the wing anyway and therefore are obviously irrelevant! Instead, call upon the good old laws of motion. The lift is upward force of the air on the wing. By principle of action and reaction (Newton's 3. law) the wing must apply force of equal magnitude and opposite direction, that is downward, on the air. Now if the ambient pressure above and below the wing is the same, this force will accelerate the air downward, which will increase its kinetic energy. And by law of conservation of energy, this energy has to come from somewhere and the only way work can be done here is by drag.
This suggests the way to reduce it. If the pressure can be increased below the wing without accelerating the air, there won't be induced drag. Well, that's exactly how ground effect reduces drag. Normally it does not eliminate it, because the air can still move outward, but a wing flying in a trench could perhaps get quite close (though not to zero, because the air still needs to move at least a bit to maintain the pressure difference).

But the air pressure is not the same above and below the wing...

@FrancisL., the pressure near the wing is not. But the ambient pressure is the pressure outside significant effect of the wing and that is the same (well, except for the pressure gradient due to density, but that is the equilibrium).

@Сократ, Try this answer of mine and the other three linked therein.

@Сократ, I'd say yes.

@Сократ, as per definitions yes, just keep in mind that in the wing tunnel you are probably in ‘ground’ effect and likely even a ‘trench’ effect, so the induced drag will be less than in free flight.

You are describing tip plates, which you see on STOL aircraft from time to time,  but which are actually too small to really do any good.  I dimly remember that for tip plates to have any noticeable effect they have to extend at least a chord width beyond the airfoil.  Because it's not just the air immediately adjacent to the tip that's curling around; it's a large package of air extending quite a distance, and to block it all takes a huge wall to get in the way.  In which case they create so much drag on their own, and create all kinds of other issues, the benefit is mostly neutralized.  Otherwise you'd see massive wing tip panels all over the place.

No, it is not possible to eliminate induced drag completely.  Many parasite drag/induced drag graphs erroneously have induced drag approaching zero.  And one certainly cannot ignore viscous effects or parasitic drag.  There is no free ride here, although it is cheaper at Vy and at higher altitudes where thinner air favors greater ground speed.
But designers do try to approach an airfoil of infinite length by designing as high an aspect ratio as possible, as in sailplane.  Also seen in nature with the albatross, this type of wing
provides the highest lift to drag ratio, but at a cost.  These wings will stall at a higher airspeed than a lower aspect ratio wing and have less stability in pitch.  The stall angle of attack is also lower.
But the performance indicates why this type of wing is most efficient, and also why props are more efficient than fans.  A wing creates lift in three ways, compression, mass deflection (action/reaction) from the bottom of the wing, and creation of lower pressure above the wing by deflection of air flow over the top of the wing.  Of these 3, the third, created by the airfoil, is most efficient.  Note, a long, thin, high AR wing will not do nearly as well with the first 2 due to pressure "leakage" from underneath, whereas a more parachute-like low AR will continue to generate more lift at a higher AOA before it stalls, just not as efficiently.  The vortex lift from deltas, ditto.
There are also design considerations as far as strength for infinite wings, but for efficient cruising, we get as close as we can with high AR.